Organic Chemistry - Amino Acids & Proteins | Organic Chemistry 25

Chad covers an entire chapter on Amino Acids & Proteins in this lesson. The lesson begins with an introduction to the general structure of alpha amino acids and to the 20 naturally occuring amino acids. Chad then explains what the isoelectric point of an amino acid is, and how to calculate it whether the amino acid has only 2 pKa values or whether the side chain has an additional pKa. An introduction to gel electrophoresis follows showing how it can be used to separate amino acids and proteins. Finally, Chad presents 3 methods of amino acid synthesis including the amidomalonate synthesis and the Strecker synthesis. Next, Chad covers peptide structure showing how peptide bonds are amides which are formed in a condensation reaction that also produces water. He also shows how disulfide bridges can form between cysteine residues showing how a covalent bond can form between potentially distant amino acids in a peptide or even between distinct peptides. He then shows how Edman degradation is used to determine the sequence of a peptide in which the N-terminal amino acid is cleaved from the peptide using phenyl isothiocyanate to form the PTH-derivative of the amino acid which is subsequently identified via gel electrophoresis or chromatography. Chad then describes the organic synthesis of peptides. He explains how a coupling reagent such as DCC can form peptide bonds between amino acids. He explains how amino groups can be protected by conversion into a carbamate, either boc or fmoc, and how carboxyl groups can be protected by conversion to either a methyl or benzyl ester. This allows formation of the peptide bond by DCC in the desired position. He then also shows how each of the protecting groups is removed after peptide bond formation. Finally, Chad shows how peptide synthesis can be automated with the Merrifield synthesis in which the growing peptide is anchored to a resin bead. The lesson is concluded with a discussion on protein structure and function. A description is provided for the four levels of protein structure: primary structure, secondary structure, tertiary structure, and quaternary structure. This includes a discussion of the planarity around the peptide bond, the structures of the alpha helix and beta sheet, and how a variety of intramolecular forces play a role in the proper folding of a protein including the hydrophobic effect, disulfide bridges, salt bridges, hydrogen bonding, dipole-dipole forces, and london forces. Several basic functions of proteins are described including enzymes which catalyze chemical reactions in living systems. 00:37 Amino Acids 12:58 Isoelectric Point (pI) 24:13 Gel Electrophoresis 28:41 Amino Acid Synthesis 35:03 Peptide Structure 39:49 Edman Degradation (Sequencing) 42:54 Peptide Synthesis 58:57 Protein Structure 1:10:37 Protein Function